Fuel supply systems, for instance, for jet engines, and particularly for those with after-burning are provided with accumulators, in order to assure feed of the necessary amount of fuel into the after-burner. For example, an amount of several liters, i.e. about 5 liters, is needed within a short time, for example, less than one second. In view of this relatively brief, high fuel requirement for the after-burner, the accumulator is intended to prevent a disturbing drop in pressure in the fuel supply system. The accumulator can comprise a rubber bag which can be filled, for instance, with nitrogen and presses the above-mentioned amount of fuel into the system upon a drop in pressure in the fuel line. As soon as the fuel system has recovered due to acceleration of the column of fuel in the feed line, the accumulator fills up again. Upon change-over from the after-burner state to the normal state of operation of the engine, the accumulator absorbs pressure peaks.
In all such fuel systems with pump feed, small variations in pressure occur (typically 0.1 bar to 0.3 bar) caused by the feed pump or else by the engine. The bag in the accumulator reacts to these variations in pressure with corresponding changes of volume, i.e. small amounts of fuel are constantly moved back and forth in the fuel supply system and are detected and processed together with the amount actually flowing to the engine. Due to the superimposition, variations in flow and measurement errors of the flow measurement system are produced.